Known energy irradiation devices for medical use include an elongate insertion portion inserted into a living body by utilizing a body lumen or through a small incision. Living body tissue, including a lesion portion, is irradiated with energy such as laser light, microwave, radio wave, and ultrasonic wave from the insertion portion, to cause annihilation of the tissue at the lesion portion through degeneration, necrosis, coagulation, cauterization or transpiration.
The energy irradiation devices are generally used to cure a lesion portion located in or in the vicinity of a skin layer of a living body tissue by irradiating the lesion portion directly with energy. These devices are also utilized for thermal therapy of a lesion portion located in a deep part of a living body tissue, such as the prostate.
In thermal therapy of the lesion portion located in a deep part of a living body tissue, it is important for the lesion portion to be heated at an appropriate temperature. To heat the lesion portion at a desired temperature, energy irradiation devices used in the past for this purpose have been designed to measure the temperature of the irradiated portion (the position of the skin portion of a living body on which the energy is incident, in the case of radiating the energy toward the lesion portion located in a deep part) and to control the output of the energy so that the measured temperature of the irradiated portion will be the desired temperature. An example is disclosed in Japanese Patent Laid-open No. Hei 7-116274 and JP-A-2002-514480 (WO 99/58194).